1. Field of the Invention
The present invention relates generally to the field of scuba diving equipment and more specifically to buoyancy compensators commonly referred to as “BC's”.
2. Background Art
In a diver's buoyancy compensator it is desirable to have the most lift (expanded volume) possible when needed yet have the least amount of bulk when it is deflated. Typically the compensator is used in a deflated or near deflated condition unless positive buoyancy is desired on the surface. The bulkier the device, the more hydrodynamic swimming resistance is created.
There are two common types of buoyancy compensator construction. The first may be referred to as a “single bag construction”. Single bag buoyancy compensators are those in which there is a single air holding cell exposed directly to the surrounding environment. The materials must be puncture resistant and very durable. Typically they have no expansive or elastomeric properties. There is one company that has a slightly expansive material, but it is expensive and of modest performance. The second type is referred to as “double bag construction”. In this configuration, an elastomeric (rubber or polyurethane) air cell is contained within an outer protective shell. By nature, elastomeric materials capable of holding air are not terribly puncture resistant or durable enough to be used without an exterior protective cover, much like an old tube type tire.
U.S. Pat. No. 5,385,496 discloses a BC having an inflatable air cell or bladder.
FIGS. 1a and 1b show the deflated and expanded cross sections of typical “single bag construction” prior art BC's with multiple non-expansive panels. Multiple panels allow the design of a more “three-dimensional shape”. FIG. 2 shows the same construction method with only two non-expansive panels.
Prior art double bag construction BC's that utilize rubber or elastomeric air cells that expand and contract are contained in a protective outer shell that usually does not expand. In some instances, a panel of expandable fabric has been incorporated in the outer shell to allow expansion, but those elastic materials are soft, of coarse weave and offer little puncture resistance. This subjects the inner air cell to damage if the outer shell is punctured through the elastic fabric panel. Prior art shows an inner expandable air cell of rubber or elastomeric material. It is enclosed in an outer shell, typically of nylon fabric. Side panels of elastic fabric mesh are sewn to the nylon shell such that the outer shell has the ability to expand during inflation. When inflated, there is considerable exposed surface area of the elastic mesh panel subject to puncture. The weave of the mesh is also at its coarsest condition during expansion, offering little resistance to puncture by sharp objects. This subjects the inner air cell to puncture, since it is not protected by the more durable nylon fabric used in the majority of the outer shell construction.